1. Field of the Invention
The present invention relates to filter presses, and in particular to continuously operating web filter presses for the removal of the liquid component from suspensions, such as, for example, from fiber-containing slurries or sludge. Presses of this kind are also particularly suitable for the removal of the water from the settling sludge obtained in sewage treatment facilities.
2. Description of the Prior Art
Continuously operating web filter presses as such are known in the prior art. Such prior art presses commonly have at least two endless filter webs with oppositely facing web portions approaching one another at an acute angle so as to define, in the area of these converging web portions, a filtering space inside which the suspension is subjected to pressure, whereby the liquid is ejected through the filter webs.
One such prior art device is disclosed in U.S. Pat. No. 1,875,075 to W. H. Mason, the device consisting of a web filter press having two endless filter webs, the filtering space being defined by oppositely downwardly slanted web portions defining an acute angle between them. After leaving this tapered filtering space, the two filter webs are guided around a drum into a horizontal run in which the material contained between the two webs is further compressed by oppositely arranged rollers. The sludge or slurry is in this case directly fed from above into the open filtering space.
This prior art device thus teaches the basic approach to the liquid removal from suspensions, inasmuch as the direction of conveyance is adapted to the changing consistency of the treated material. The latter, as long as it has the consistency of a flowable liquid, is confined between substantially upright web portions within the funnel-shaped filtering space, and as its consistency becomes semi-solid or solid, the direction of conveyance is changed to the more convenient horizontal mode. In this horizontal run the material is further compressed to a cake.
Practical applications of this known web filter press are found primarily where the liquid is to be removed from fiber suspensions. It has also been found that the efficiency of liquid removal, i.e. the degree of drying obtainable, is insufficient for various other applications.